Installing software

In this chapter we will go over installing and setting up all software required for AQLARP to work. You should already have AQLARP's GitHub repo cloned in your home directory as specified in chapter 4.1

Installing ros2

AQLARP is built using ros2 iron, it might work with later versions but this is untested. To install ros2 iron you can follow their installation instructions. After installing ros2 you must also install colcon, which is ros2's build system. To do this run the command below.

$ sudo apt install python3-colcon-common-extensions

Sourcing ros2 automatically

To use ros2 you must source it every time, which can be annoying. To do this automatically run the following command.

nano ~/.bashrc

Then add these 2 lines at the end of the file.

source /opt/ros/iron/setup.bash
source ~/new_ws/install/setup.bash

Then press Ctrl + O to save and Ctrl + X to exit. To make this apply you should log out of the Raspberry Pi and start a new shell session.

Installing dependencies

To install dependencies first go into the workspace directory. To do this run the following command.

$ cd ~/AQLARP/ros2_ws

Then run the following command to install all required dependencies using rosdep.

$ rosdep install --from-paths src -y --ignore-src

Then additionally you have to install pygame using pip, since the version rosdep uses is severally outdated. To do this run the following command.

$ python3 -m pip install pygame

Building the code

You should be in the workspace directory as specified in the previous step. Then to build the code run the following command and wait for it to complete

$ colcon build

Calibrating the servos

Since the servos aren't exactly at 90° they have to be calibrated. To run the calibration script run the following command.

$ ros2 run aqlarp_motors calibration

Then to use the calibration script use the left and right arrow keys to increase or decrease the angle offset and use the up and down arrow keys to switch servo. You should try to set all servos as close to 90 degrees as possible.

Running the code

To run all code of AQLARP, and thus start the robot, run the following command.

$ ros2 launch aqlarp_main aqlarp.launch.py

To control the robot you will have to connect a ps4 controller. You can either do this by using a cable and connecting it using one of the USB ports, or alternatively you can use the instructions in the next part to connect the ps4 controller wirelessly.

The controls for AQLARP are as follows:

Playstation button: start and stop the servos
Left Joystick: Make the robot strafe in the direction you specify
Right Joystick: Make the robot turn by moving the joystick left and right.

Connecting ps4 controller wirelessly

Open a command prompt on the raspberry pi (with ssh) and run the following command to get into the Bluetooth command line.

$ bluetoothctl

Then start scanning for Bluetooth devices with the following command.

scan on

Now press and hold the PlayStation and share button on your controller for a few seconds until the lightbar starts flashing. Then look at the output in your terminal for something like this.

Device A4:AE:11:41:FD:98 Wireless Controller

Copy the MAC address (the numbers in the center) and run the next command to pair with the controller. Make sure the lightbar is still flashing, if it isn't flashing anymore hold down the PlayStation and share button again.

pair <MAC address>

Then finally to make it so the controller can connect to AQLARP by just pressing the PlayStation button, run

trust <MAC address>

Now type exit to exit the Bluetooth terminal. If you want to disconnect the controller, hold down the PlayStation button for 10 seconds. To reconnect the controller, press the PlayStation button once.

Making the code run on startup

If you want to make AQLARP's code run on startup so you can just connect the controller and use it, you will have to create a file called aqlarp.service at /etc/systemd/system/. To do this run the following command.

$ sudo nano /etc/systemd/system/aqlarp.service

Then paste the following content into it.

[Unit]
Description="AQLARP daemon"

[Service]
User=AQLARP
Restart=always
RestartSec=1

Environment="LD_LIBRARY_PATH=/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_interfaces/lib:/opt/ros/iron/lib/aarch64-linux-gnu:/opt/ros/iron/lib"
Environment="PYTHONPATH=/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_sensors/lib/python3.10/site-packages:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_motors/lib/python3.10/site-packages:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_main/lib/python3.10/site-packages:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_interfaces/lib/python3.10/site-packages:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_input/lib/python3.10/site-packages:/opt/ros/iron/lib/python3.10/site-packages"
Environment="AMENT_PREFIX_PATH=/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_sensors:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_motors:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_main:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_interfaces:/home/AQLARP/AQLARP/ros2_ws/install/aqlarp_input:/opt/ros/iron"

ExecStart=/opt/ros/iron/bin/ros2 launch aqlarp_main aqlarp.launch.py

[Install]
WantedBy=multi-user.target

If you use a different user than AQLARP or have cloned the GitHub repo in a different location, you will have to edit this file accordingly. To save the file press Ctrl + O and then press Ctrl + X to save.

Then finally to enable the service, run the following command.

$ sudo systemctl enable --now aqlarp.service